A portafilter or holder for a coffee pod, although of course it is usable with a filter and charge of loose coffee, comprises a cup typically having a handle and formed in its floor with an outlet port. The pod itself is normally made as a short cylindrical pad filled with ground coffee and having a flange forming a radial extension of its planar upper face. In use the pod is dropped into the cup of the portafilter, the portafilter is fitted to the group head, and hot water is forced down through the pod at a pressure of 1.5 bar to 2 bar, so that the desired infusion-coffee-drips from the outlet port into one or two cups sitting underneath it.
As described in U.S. Pat. No. 6,021,705 of Dijs, the holder is formed in its floor with an array of radially extending and upwardly open grooves that terminate at the central port. Thus the liquid exiting the bottom of the pod runs along these grooves to the port, whence it drips out of the holder.
A disadvantage of this system is that the coffee produced by it does not have the froth or crema that is made by a standard commercial or pressurized system using loose ground coffee that is tamped in the holder. The lack of such crema, which increases the aroma of the espresso thus produced, is considered a serious failing by coffee afficionados. In addition the holder is particularly hard to clean, especially once the grooves develop lime deposits.
A so-called perfect-crema disk has been proposed for use in a coffee holder. It is a rubber disk with an aperture and serves mainly to increase back pressure on the grounds held in the pod. Such an accessory is largely ineffective in producing good crema, and is itself a bothersome item to deal with and maintain clean.